Apparatus and method for performing a continuous chromatographic analysis



Dec. 24, 1968 D. w. THOMPSON 3,417,548

APPARATUS AND METHOD FOR PERFORMING A CONTINUOUS CHROMATOGRAPHIC ANALYSIS Filed Sept 15, 1967 2 Sheets-Sheet;

INVENTOR:

D. W. THOMPSON HIS ATTORNEY 1968 D. w. THOMPSON 3,

APPARATUS AND METHOD FOR PERFORMING A CONTINUOUS CHROMATOGRAPHIC ANALYSIS Filed Sept. 15, 1967 2 Sheets-Sheet 2 IIIII k FIG. 4

INVENT OR:

D. W. THOMPSON BY- HIS ATTORNEY United States Patent APPARATUS AND METHOD FOR PERFORMING A CONTINUOUS CHROMATOGRAPHIC ANALYSIS Donald W. Thompson, Oakland, Calif., assignor to Shell Oil Company, New York, N.Y., a corporation of Delaware Filed Sept. 15, 1967, Ser. No. 667,969 3 Claims. (CI. 5567) ABSTRACT OF THE DISCLOSURE A continuous chromatographic unit using two closely spaced parallel surfaces with at least one of the surfaces being rotated. One of the surfaces is coated with nonvolatile or solid material that serves as the partition phase while the carrier gas is fed from a first inlet and the feed vapor is injected slightly downstream from the first inlet. The different components of the feed vapor are removed at different locations around the periphery of the surfaces.

Background of the invention.Chromatographic devices are used throughout industry to separate fluid streams into their basic components. At the present, all chromatographic devices are of the batch type in which a sample of material is injected into the chromatographic column and then swept through the column by a carrier gas. This type of operation is satisfactory where the chromatographic column is used as an analytical device, but is not satisfactory where the chromatographic column is used as a monitor device for a continuous process.

It can be readily appreciated that in a continuous process it is desirable to have a continuous reading of the components of the process stream being monitored. When the present chromatographic devices are used, a sample of the stream must be obtained and then injected into the chromatographic column and analysis obtained. Thus, the system is a batch type of monitoring and has considerable time delay between the time the sample is obtained and the results of the analysis are known.

The use of chromatographic columns in control processes has increased substantially, since they provide the most efficient means for obtaining a detailed analysis of a process stream in a chemical or petroleum process. Of course, the analysis is satisfactory if the only information desired is an analysis of the stream. It is not satisfactory if the analysis is performed to obtain data for use with an automatic control system. The combination of a batch type of analysis and the time delay in the chromatograph unit results in an overall time lag that is undesirable. 'In the case of an automatic control system the time delay, while presently tolerated, is not desirable.

Summary of the inventi0n.The present invention solves the problem of a batch type of process for chromatographic columns by providing a continuous chromatographic separation. More particularly, the invention utilizes two closely spaced surfaces with at least one of the surfaces being coated with a partition material. The carrier gas is then injected into the space between the two surfaces at a first point while the fluid to be analyzed is injected in the form of a vapor downstream from the point at which the carrier gas is injected. The carrier gas then sweeps the sample vapor through the space between the two surfaces, while at least one of the surfaces is rotated with respect to the flow of the carrier gas and sample vapor. The separated components of the vapor sample are collected at the outer edge or periphery of the two surfaces and then passed to a suitable detecting device such as that used in conventional chromatographic units.

While the two surfaces may take various shapes, as

3,417,548 Patented Dec. 24, 1968 for example two cylinders that are mounted coaxially with the carrier gas and vapor sample being injected between the space between the two cylinders, a simplified arrangement can be easily fabricated from two discs. The discs are closely spaced and disposed so that one disc may be rotated with respect to the other. The surface of at least one of the discs is coated with a nonvolatile partitioning material, the type of material depending upon the vapor sample that is to be separated into its individual components. The carrier gas is injected at the center of the discs with the vapor sample being injected at a point slightly displaced from the center. The various components will assume various angular displacements from the point at which the vapor sample is injected and can be collected and passed to a detector.

Brief description of the drawings.The above advantages of this invention and its construction will be more easily understood from the following detailed description of a prefered embodiment when taken inconjunction with the attached drawings in which:

FIGURE 1 is a plan view of the chromatographic device constructed according to this invention;

FIGURE 2 is a vertical section of the device taken along line 2--2 of FIGURE 1;

FIGURE 3 shows a partial vertical section of a modified form of the chromatographic device shown in FIG- URES 1 and 2; and

FIGURE 4 shows a vertical section of modified form of the chromatographic device shown in FIGURE 1.

Description of preferred emb0diments.-Referring now to FIGURES 1 and 2, there is shown a plan view and vertical cross section of a continuous chromatographic device constructed according to this invention using two rotating discs. More particularly, the upper disc 10 and the lower disc 11 are closely spaced. The lower disc is fixedly mounted, while the upper disc is rotatably mounted in suitable bearings, not shown. In addition, the upper disc is mounted with a fixed distance between the two discs as explained below. The lower disc is provided with an inlet 18 through which the carrier .gas is admitted as explained below. The upper disc is provided with a drive shaft 14 extending downwardly that is connected to a suitable drive means not shown in the attached drawing. The drive means is preferably a variable-speed drive means in order that the speed of rotation of the disc may be varied from approximately one quarter rotation per second to three or four rotations per second.

The lower surface 17 of the upper disc is coated with a suitable nonvolatile partitioning material. In the alternative the partitioning material may be a solid which is deposited upon the lower disc. The patricular partitioning material used will depend upon the composition of the feed vapor and the separation desired, although the same partitioning materials as are used in conventional columntype gas chromatographic devices can be used with the present invention. The carrier gas is introduced through the inlet 18 into the interior 16 of a cup-shaped recess formed in the lower disc. A suitable rotating seal 21 is positioned in the recess and surrounds the shaft 14. The seal may be any gas-tight seal, for example, a mercury seal is preferred, since it provides an effective gas-tight seal between the stationary carrier gas inlet and the rotating shaft. The feed vapor is introduced through a conduit 23 whose end 24 is displaced radially outward from the carrier gas inlet. The important feature to be considered in mounting the vapor feed conduit is that the inlet is positioned downstream from the inlet of the carrier gases to insure that the carrier gas will sweep the vapor feed into the space between the two discs.

'In some applications it may be desirable to provide a heating means for heating the space between the two discs to increase the speed of separation of the various components. The heating means may be easily provided by utilizing resistance heating wires that are mounted in the space between the two discs or may be embedded in the surface of the lower discs as shown. The outer ends of the resistance heating wires are connected to terminals 31 and 32 at the outer periphery of the discs.

Example.lf it is desired to separate normal pentane from normal hexane with no overlap, one could select two discs having about 18 cm. diameter and a spacing of 100 microns. One of the discs could then be coated with silicon oil having approximately .25 micron thickness and the discs rotated at about 4 radians per second to effect separation between the pentane and the hexane. Under these condition, n-pentane would exit from the discs at a point about 25 from the point at which the sample was introduced as illustrated by the dotted lines 35 while n-hexane would exit at an angle of 42 as illustrated by the lines 34. Thus, the two components exit at different angles and separation would be effected. The discharged components could be collected by suitable means positioned at approximately the positions shown by the dotted lines 34 and 35. The collected samples can be supplied to conventional chromatographic detectors, for example in the case of n-pentane/n-hexane, a flame-ionization detector could be used. The collecting means and detecti'ng means are not shown in FIGURE 1, since these are known to those skilled in the art.

Description of modified emb0diments.A modified form of the invention is shown in FIGURE 3 in which an adsorbent material 40 is mounted on the lower surface of the upper stationary disc '10 with the partitioning material being disposed on the adsorbent material. In addition, the two discs are not rigidly connected together, but provisions are made for both oscillating and rotating the lower disc 11 so that its upper surface moves toward and away from the surface of the adsorbent material as the discs rotate. The oscillation of the lower disc can be obtained by providing either a mechanical means that cooperates with the drive means or an electromechanical means that oscillates the disc. The oscillation of the lower disc increases the efficiency of the separation by increasing the effective surface area of the partitioning material, thus enabling a greater amount of vapor to be separated and providing a more useful signal for the detector. The adsorbent material may take various forms, as for example the material commonly used for packing chromatographic columns may be used for the adsorbent material and normal partitioning materials disposed thereon,

An alternate arrangement can be provided by using a sintered metal disc and disposing the partitioning material thereon. The lower disc is then oscillated to cause the carrier gas and vapor sample to flow in and out of the sintered metal disc. The flow in and out of the sintered metal disc will increase the effective area of the partitioning material.

Shown in FIGURE 4 is a modified form of the invention that is particularly useful when a large number of samples requiring different partitioning materials are to be analyzed. The modification consists of substituting a thin disc for the rigid upper disc 10 shown in FIG- URE 1. The thin disc may have a rigid center section 52 that is secured to the drive shaft by a nut 51. The thin disc is coated with the partitioning material that permits changing the material by changing the discs.

When the chromatograph is operated, the thin disc is rotated and the carrier gas introduced. The disc will then assume a position close to the rigid lower disc as a result of the centrifugal force and the gas flow will prevent physical contact between the discs. Also while the heating means are shown incorporated in the lower disc in FIGURE 1, when thin discs are used, radiant heat may be substituted for the resistance heating shown in FIG- URE 1.

While the present invention has been described with relation to embodiments utilizing rotating discs as explained above, one could also use rotating cylinders. The important feature of the invention is the providing of two closely spaced surfaces and the injecting of both the carrier gas and the vapor feed into the space between the two surfaces. At least one of the surfaces are then rotated with respect to the normal flow of the gas to effect the separation of the various components from the feed vapor. Further, one of the surfaces is coated with a partition material of the type commonly used in chromatographic columns to effect the separation.

I claim as my invention:

1. A continuous chromatographic device comprising a pair of closely spaced discs, said discs being mounted in juxtapositons so that the surface of one disc may rotate relative to the surface of the other;

rotating means coupled to said discs to rotate at least one of the discs about its axis and at least the surface of one of said discs being coated with a nonvolatile partition material;

an oscillating means disposed to oscillate one disc in a direction parallel to its axis;

a first inlet mean, said inlet means being disposed to communicate with the space between said discs adjacent the center of rotation of the discs;

a source of carrier gas, said source of carrier gas being connected to said first inlet means;

a second inlet means, said second inlet means communicating with the space between the discs at a position displaced downstream from the first inlet means;

a source of feed vapor, said source of feed vapor being coupled to said second inlet means; and

means disposed around the periphery of said discs to remove the different components of the feed vapor.

2. A method of performing a continuous chromatographic analysis comprising:

introducing and flowing a stream of carrier gas between two juxtaposed, closely spaced surfaces, one of said surfaces being coated with nonvolatile partition material;

introducing and flowing a feed vapor between the two surfaces at a point displaced downstream from the point of introduction of said carrier gas;

rotating at least one of said surfaces with respect to said carrier gas and feed vapor flows and oscillating one surface along an axis perpendicular to the surface; and

removing the separated products of the feed vapor at the outer edge of said surfaces.

3. A continuous chromatographic device comprising:

a pair of discs, one of said discs being thin and flexible, the other being rigid, the surface of at least one of said discs being coated with a nonvolatile partition material, said discs being mounted in juxtaposed positions so that the surface of one disc may rotate relative to the surface of the other;

rotating means coupled to said thin disc to rotate it about its axis whereby the spacing between the discs is in part determined by the centrifugal force on the thin discs;

at first inlet means, said inlet means being disposed to communicate with the space between said discs adjacent the center of rotation of the discs;

a source of carrier gas, said source of carrier gas being connected to said first inlet means;

a second inlet means, said second inlet means communicating with the space between the discs at a position displaced downstream from the first inlet means,

a source of feed vapor, said source of feed vapor being coupled to said second inlet means; and

means disposed around the periphery of said discs to remove the different components of the feed vapor.

(References on following page) 5 6 References Cited FOREIGN PATENTS UNITED STATES PATENTS 636978 2/1962 Canada- 3 07g 47 2 19 3 Mosier 55 197 REUBEN FRIEDMAN, Primary Examiner.

3,016,106 1/1962 Luft 55-197 I. DE CESARE, Assistant Examiner. 

